INTRACAVITARY FILLING PATTERN IN THE FAILING LEFT-VENTRICLE ASSESSED BY COLOR M-MODE DOPPLER-ECHOCARDIOGRAPHY

Objectives. The present study aimed to investigate the mechanism of in tracavitary changes in filling pattern during acute ischemic left vent ricular failure and during beta-adrenergic blockade, Background. Recen t clinical studies with color M-mode Doppler imaging have shown abnorm al intracavitary filling patterns in the diseased ventricle. Methods. In open chest anesthetized dogs with intracardiac micromanometers and myocardial segment-length crystals, global ischemic left ventricular f ailure was induced (n = 8) by coronary microembolization. In nonischem ic ventricles inotropy was decreased (n = 6) by intravenous propranolo l and increased (n = 6) by intravenous isoproterenol. From color M-mod e Doppler images we calculated the time difference between peak early diastolic filling velocity at the mitral tip and apex using computer a nalysis. The time difference of peak velocity was used as an index of the timing of apical filling. Results. There was marked retardation of apical filling with microembolization and propranolol. Time differenc e of peak velocity increased from 20 +/- 6 (mean +/- SEM) to 101 +/- 1 7 ms (p < 0.05) and from 21 +/- 8 to 80 +/- 18 ms (p < 0.05), respecti vely. Time constant of isovolumic relaxation increased from 34 +/- 3 t o 43 +/- 5 ms (p < 0.05) and from 31 +/- 1 to 39 +/- 3 ms (p < 0.05) d uring microembolization and beta-blockade, respectively. Isoproterenol tended to cause the opposite changes, Time difference of peak velocit y showed a positive correlation with time constant of isovolumic relax ation (r = 0.89, p < 0.01) and a negative correlation with peak early transmitral pressure gradient (r = 0.88, p < 0.01). In the intact left ventricle, peak apical filling velocity coincided with peak early tra nsmitral pressure gradient. During ischemic failure, however, peak api cal filling velocity occurred 53 +/- 14 ms after peak early transmitra l pressure gradient had decreased to zero and at a time when transmitr al flow had ceased, suggesting a change in intraventricular flaw distr ibution. Conclusions. Color M mode Doppler imaging revealed retarded a pical filling during depression of myocardial function by global myoca rdial ischemia or beta-blockade. The abnormal filling pattern may be a sign of impaired left ventricular relaxation.